In the prior art it has been necessary to have a skilled craftsperson and a transmission test set at each end of a circuit under test. The skilled craftspeople manually operated each instrument and recorded data. Coordination of the test effort frequently required an additional unused circuit and the test effort frequently proved tedious, time-consuming and produced inconsistent results.
The invention provides a portable transmission impairment measuring instrument capable of operating as a MASTER or SLAVE unit and requiring only the circuit under test for communication. A microprocessor in the MASTER unit automatically controls operation of the MASTER unit and a SLAVE unit at each end of a line under test in accordance with preprogrammed micro-instructions stored in a read only memory.